Conventionally, the measurement of the amount of an analyte in a sample using a redox reaction has been utilized for a wide range of applications. For example, such measurement has been utilized for measuring glycated amines (glycated proteins, glycated peptides, glycated amino acids, etc.) in applications such as biochemical analyses, clinical tests, and the like.
In particular, glycated proteins in blood, especially glycated hemoglobins in erythrocytes, serve as important indexes in the diagnosis, treatment, etc. of diabetes, because they reflect the patient's past history of blood glucose levels. Such glycated proteins in erythrocytes are measured using a redox reaction, for example, in the following manner.
First, erythrocytes are hemolyzed to prepare a sample. Then, a fructosyl amino acid oxidase (hereinafter referred to as “FAOD”) is added to this hemolyzed sample. The FAOD acts on a glycation site of a glycated protein to cause a redox reaction, thereby forming hydrogen peroxide. The amount of the hydrogen peroxide corresponds to the amount of the glycated protein. Subsequently, a peroxidase (hereinafter referred to as “POD”) and a reducing agent that develops color by oxidation are added to the sample so that a redox reaction occurs between the hydrogen peroxide and the reducing agent with the POD as a catalyst. This redox reaction causes the reducing agent to develop color, and the amount of the hydrogen peroxide can be determined by measuring the color developed. As a result, the amount of the glycated protein in the erythrocytes can be determined.